Heating hydrocarbon fluids



` May 4, :1937.

W. E. LOBO HEATING HYDROCARBON FLUIDS Filed Nov. ie, 1934 ll ll ll llINI/EN TOR. WALTER E. LOBO www@ A TTORNE Y Patented May 4, 1937 STATESUNITED ao'zazis HEATING HYDROCARBON FLUIDS Walter E. Lobo, Westfield, N.J., assigner to Gasoline Products Co., Inc., Newark, N. J., `acorporation of Delaware y Application November 16, 1934, Serial No.753,257 v2 claims. (ci. 19e- 4.7)l

This invention relates in general to the heating of hydrocarbon fluidsand more especially to heating hydrocarbon fluids to elevatedtemperatures in a rapid manner by providing a lar-ge ratio of heatingsurface to the volume of hydrocarbon fluid being heated.

More specifically, this invention relates to improvements in heating.hydrocarbon iiuds in an apparatus wherein a multiplicity of parallelpaths are provided for a stream of hydrocarbo-n fluid to thereby greatlyincreasethe amount of heating surface available for a given quantity ofiiuid being heated at any one time.

In the heating ofl hydrocarbon iiuid to elevated temperatures, such ascracking temperatures, it is often desirable to heat the iiuid to therequired temperature as rapidly as possible. By rapidly heating thehydrocarbon fluid to the desired temperature, it is possible to carryout `the desired reaction without the disadvantages that mightilow fromcontinuously heating the hydrocarbon fluid, to the desired temperaturefor a prolonged A,period kof time.

x In accordance `with my invention, a stream of hydrocarbon vfluid is`preferably preheated to anelevated temperature, 4but to a `temperaturewhere inappreciable cracking occurs. This heatingmay be accomplished ina convection heating chamber of ,a v'furnace receiving combustion gasesfrom thecombustion or radiant heating chamber. The combustion or radiant'heating chamber, as contemplated by my invention, is provided with amultiplicity of heat-absorbing 'tubes on` each wall which cover at leasta portion of each wall and preferably the majority "thereof,'with Aallof the tubes on any one wall being-connected in parallel. Y c

The preheated stream of hydrocarbon fluid from the' convection `heatinglchamber is introduced, as contemplated by my invention, `into amanifold which is connected with the parallel arrangedtubes in thecombustion chamber. The hydrocarbon fluid flows from Vthe manifold in a`multiplicity of much `smaller streams, `as determined by the number roftubes connected in parallel ,tol themanifold', through the lcombustionAor lradiant heating chamber. By Adividing thefmain stream of`hydrocarbon :fluid into a Amulti'plicityof smaller streams for'passage,say once, in small 1 tubes around the combustion {chamberythere isprovidedl a much larger ratio idf-itube surface, that vis,'heatingsurface, toV tube volume; that is, volume `of hydrocarbon fluid in any4onetube,vvhichfresults in much more rapid heatingwof; the:l hydrocarbonfluid" `than would be the case if the preheated stream was caused toflow progressively and serially through larger tubes arranged on theWalls and/or roof of the combustion chamber in the conventional mannerin order to accomplish the desired heating of said hydrocarbon fluid. Itwill `thus be apparent that each of the multiplicity o-f small streamsis individually heated to an elevated temperature during the passage ofeach stream in the tubes around the walls defining the combustion orradiant heating chamber.

My invention further contemplates a plurality of tubes connected inparallel and disposed upon the roof of the combustion or radiant heatingchamber. These roof tubes are preferably utilized for passing a secondstream of oil therethrough to be heated to the desired elevatedtemperature, the same fundamental principle being applied to this streamas the other, that is, providing a large ratio of heating surface tohydrocarbon fluid volume to thereby make possible the more rapid heatingof this stream of hydrocarbon uid.

In order to make my invention more clearly Y understood, I have shown inthe accompanying drawing, means for carrying the same into practicaleffect Without limiting the improvements in their useful application tothe particular construction which, for purposes of explanation, has beenmade the subject of illustration.

In the drawing:

Figure 1 is an elevational View, partly in section, o-f an apparatusembodying my invention.

Figure 2 is a plan View of part of the apparatus taken along line 2-2 ofFigure l.

Referring to the drawing wherein like parts in the two views aredesignated by the same characters, and more particularly to Figure 1,there is shown a furnace setting I having a combustion or radiantheating chamber 2 and a convection heating chamber 3, the chambers 2 and3 being separated from each other by `a bridge wall '4. The combustionchamber 2 is provided with a plurality of burners 5 disposed in anysuitable manner but preferably in the two side Walls and the-end wallthereof. The hot products of combustion produced by the burners 5passupwardly through the chamber 2, over the bridge wall 4, through theconvection `heating chamber 3 and are withdrawn from the convectionheating chamber 3 through a flue 6 leading to a suitable stack, notshown.

Hydrocarbon fluid to be heated to an elevated temperature is introducedVinto a line 1 from which it is passed to a plurality of interconnectedtubes 8 disposed in the convection heating chamber 3 in such a manner asto be swept by the hot combustion products passing therethrough. Theindividual tubes 8 have been shown as connected in series, although itis to be clearly understood that these tubes may be connected inparallel if desired. The hydrocarbon fluid passing through theheat-absorbing tubes 8 is preheated therein to an elevated temperature,preferably to a temperature Where inappreciable cracking occurred. Thethus preheated hydrocarbon fluid aiter passing through theheat-absorbing tubes 8 is conducted by means of a line 9 to thecombustion chamber 2.

The hydrocarbon fluid passing through the line 9 is introduced into amanifold II shown as positioned in the combustion chamber 2, although itmay be outside thereof. The combustion or radiant heating chamber 2 isprovided with a multiplicity of heat-absorbing tubes I2, preferably ofsmall internal diameter, which eX- tend around the four walls of thecombustion chamber 2 to form a heating coil. As contemplated by myinvention, the tubes on each wall which form a partI of the coil sectionare connected in parallel, that is, the hydrocarbon fluid introducedinto the manifold II is divided into a plurality of streams, each ofWhich passes through an individual tube I2. The tubes I2 forming thecontinuous path for each parallel path of hydrocarbon fluid areconnected at the corners of the furnace setting by suitable 90 returnbends i3. It Will be evident from the foregoing that the oil leaving themanifold II is divided into a multiplicity of parallel streams forpassage through the tubes I2 extending once around the combustionchamber 2. By dividing the main Stream of hydrocarbon iluid into amultiplicity of parallel streams in the manner shown, there is provideda much larger ratio of heating surface to hydrocarbon fluid volume thanwould otherwise be the case.

The hydrocarbon fluid after passing as separate streams through theparallel tubes I 2 on .i the back Wall of the furnace is conducted to amanifold Ill, also shown as positioned within the combustion chamber 2although it may be on the outside, wherein it may be quenched, fromwhich the heated stream of hydrocarbon fluid is Withdrawn through a lineI5 for passage to other equipment, such as a soaking chamber orevaporator, for further treatment.

The hydrocarbon fluid passing through the heat-absorbing tubes I2 israpidly heated to an elevated temperature, such as to the desiredcracking temperature, preponderantly by the radiant heat absorbed by thetubes.

It will be noted that the parallel arranged tubes on each of the Wallsdefining the combustion chamber cover the majority thereof and all ofthe tubes on any one Wall are connected in parallel. It will be apparentthat the furnace setting may be enlarged in order to provide sufcientspace for another heating coil similar to the heating coil composed ofthe tubes I2 but disposed either above or below the tubes I2. Thus itwill be possible in accordance with this modification to provide stilladded heating surface for the hydrocarbon uid being treated.

My invention further contemplates the heating of a second stream ofhydrocarbon uid in the apparatus described. As shown, there is provideda multiplicity of roof tubes I6 connected in parallel. This group oftubes is connected to a manifold at each end thereof, the stream offluid flowing in parallel paths through these tubes.

The second stream of hydrocarbon fluid may be passed through a line IIinto a manifold I8 disposed adjacent the roof and the side Wall of thefurnace setting shown in Figure 1. This stream of hydrocarbon fluid isdivided into a multiplicity of parallel streams for passage through thetubes I8. From the tubes I6 the parallel streams enter a manifold, notshown, but similarly disposed on the other side of the furnace setting,and in which the hydrocarbon fluid may be quenched. From this manifoldthe hydrocarbon iluid is conducted through a line, not shown, tosuitable equipment, such as an evaporator or a soaking chamber forfurther treatment.

The second stream of fluid passing through the groups of parallelconnected tubes I6 is heated to elevated temperature preponderantly bythe radiant heat absorbed by these tubes, although it will be evidentthat these tubes also receive some convective heat.

If desired, separate groups of parallel connected tubes disposedadjacent the roof of the chamber 2 may be provided each group for amanifold at each end, and the groups connected between manifolds by asuitable line.

Ii desired the group of roof tubes I6 may be dispensed with therebyleaving the roof of the furnace bare. By having both a bare roof and abare iloor, it Will be evident that reflected or re-radiated heat fromboth of these surfaces is possible. Consequently the group of parallelarranged tubes I2 receives not only the direct radiation from theproducts of combustion passing through the combustion chamber 2 but alsore-radiation from both the floor and roof of the furnace setting.

When the groups oi tubes I6 are not included in a heating apparatus inaccordance with my invention, the parallel arranged tubes I2 on the fourWalls of the combustion chamber 2 may be arranged around the horizontalaxis of this chamber instead of the vertical axis as shown.

Thus, these groups of tubes may be disposed on the floor and roof of thecombustion chamber connected by vertical tubes on each of the sideWalls. With this arrangement, as in the other,

all of the tubes are connected in parallel so that the hydrocarbon fluidpasses only once around the combustion chamber. It will be apparent withthis arrangement that the front wall and the bridge Wall are bare,burners being disposed in the front wall with the products of combustiontraveling horizontally from the burners to the bridge wall, thusexposing all the tubes to substantially the same degree of heat. Thebridge wall may be provided With suitable openings for passage of theproducts of combustion to the convection heating chamber.

In operating in accordance with my invention, a relatively clean gas oilstock may be passed through the preheating tube 8 and therein raised toa temperature short of cracking, say to a temperature of about 800 F. orabove. The oil after being preheated in the tubes 8 is passed throughthe parallel connected tubes I2 wherein it is rapidly raised to a highcracking temperature, such as to a temperature about 1l00 F'. or higher,preponderantly by radiant heat absorbed by these tubes. Preferably thisstream of oil is maintained under a super-atmospheric pressure, forexample, from 750 to 4500 pounds per square inch.

A second stream of oil, such as a reduced crude,

preferably preheated, may be introduced into the line I1 and passedthrough the groups of parallel connected tubes I6 to therein be raisedto a temperature sufficiently high to accomplish the desired viscositybreaking thereof, as for example, to a temperature of about say 925 F.while being maintained under a pressure of, say, from 50 to 750 poundsper square inch.

It will be noted that my invention avoids connections between theheating coil on the four walls of the combustion chamber and the heatingcoil adjacent the roof. While a connection may be provided for conveyingthe hydrocarbon fluid from the four wall heating coil to the roofheating coil, or vice-versa, I prefer not to make such provision in Viewof the uncontrolled cracking that may take place insuch a connectionwith the resultant coke deposition therein.

The number of parallel tubes I2 comprising the heating coil in thechamber 2 may be varied depending on the amount of heating surfacerequired to raise the oil to a given temperature in a specified time.While I have shown a certain number of parallel connected tubes on eachwall, this is merely for illustrative purposes. For instance, the numberof parallel connected tubes may vary considerably as from about 20 or 30to about 150 or more.

It may be desirable in some instances to dispose a group of tubesVconnected in parallel on only part of the walls in the combustionchamber.

For instance, parallel connected tubes may be disposed on only two ofthe walls, the other two being left bare, or if desired, all of thewalls may be covered at least in part with parallel connected tubes anda separate stream of hydrocarbon fluid passed through the tubes on oneor more of the walls.

From the foregoing it will be readily appreciated that the variousstreams of oil heated in an apparatus of the type shown are heated at amuch more rapid rate than otherwise would be the case. By providing amultiplicity of parallel tubes, a much larger ratio of tube surface totube volume is made possible, thereby greatly increasing the rate ofheat input tothe oil.

The tubes in the combustion chamber 2 are preferably of small internaldiameter. For in- Stance, in constructing an apparatus of the typeshown, tubes having an internal diameter of about three-eighths of aninch to one inch or higher may be used.

Obviously many modifications will suggest themselves to those skilled inthe art, and my invention should be limited only by the limitationsimposed in the appended claims, where the true scope thereof is defined.

I claim:

l. The method of heating hydrocarbon fluids to a cracking temperature inan apparatus comprising a combustion chamber, a separate convectionheating chamber supplied with furnace gases from the combustionchamber,a singlepassage heating coil disposed in the convection heating chamber,andV a parallel-passage heating coil disposed in a horizontally arrangedbank within the space constituting the Acombustion chamber about thewalls thereof and substantially out of the path of the convection gasesflowing to the convection chamber, each of the tubes of whichparallel-passage heating coil is of smaller cross-sectional area thanthat of the single-passage heating coil, that comprises first heatingthe hydrocarbon fluid in a single continuous stream in thesingle-passage heating coil in said convection heating chamber andthereafter dividing all of the stream from the convection heatingchamber directly into a plurality of continuous streams flowing throughthe tubes of the parallel-passage heating coil, so that the hydrocarbonfluid flowing in parallel streams in the tubes entirely around the wallsof the combustion chamber is heated preponderantly by radiant heat in aplurality of parallel streams of reduced cross-sectional area.

2. 'I'he method of heating hydrocarbon fluids to a cracking temperaturein an apparatus comprising a combustion chamber, a separate convectionheating chamber supplied with furnace gases from the combustion chamber,series connected tubes comprising a heating coil disposed in theconvection heating chamber, and a parallel-passage heating coil disposedin a bank extending entirely around four of the boundaryy surfaces ofthe combustion chamber and substantially out of the path of theconvection gases flowing to the convection chamber, each of the tubes ofwhich parallel-passage heating coil is or" materially smallercross-sectional area than the tubes of the flrst-mentioned heating coil,that comprises first heating the hydrocarbon fluid in the lheating coilin said convection heating chamber and thereafter dividing all of saidhydrocarbon fluid from the convection heating chamber directly into aplurality of continuous streams flowing through the tubes of theparallel-passage heating coil, so that the hydrocarbon fluid ilowing inparallel streams inV the tubes entirely around the combustion chamber isheated preponderantly by radiant heat in a plurality of parallel streamsof reduced cross-sectional area.

WALTER E. LOBO.

